Microstructure, chemical composition, wear, and corrosion resistance of FeB–Fe2B–Fe3B surface layers produced on Vanadis-6 steel using CO2 laser

Abstract

The paper presents the study results of laser modification of FeB-Fe 2 B surface layers produced on Vanadis-6 steel using pack cementation method. Microstructure, x-ray phase analysis, chemical composition study using wave dispersive spectrometry method, microhardness, corrosion resistance as well as surface condition, roughness, and wear resistance were investigated. The diffusion boronizing processes were performed at 900°C for 5 h in the EKabor® powder mixture. The boronized layers had a dual-phase microstructure composed of two types of iron borides, FeB and Fe 2 B, and their microhardness ranged from 1800 to 1400 HV. The laser surface modification was carried out on specimens after diffusion boronizing process using CO 2 laser with a nominal power of 2600 W. Laser beam power used in this experiment was equal to 1040 W and was constant. While the three values of scanning speed were used: 19, 48, and 75 mm/s. During laser modification, the multiple tracks were made where distance between of axis tracks was equal to 0.5 mm. As a result of this process, microstructure consisted of remelted zone, heat-affected zone, and substrate was obtained. In remelted zone, the boron-martensite eutectic was observed. Boronized layers after laser modification were characterized by the mild gradient of microhardness from surface to the substrate and their value was dependent on the scanning speed used and was between 1700 and 1100 HV. Corrosion resistance tests revealed reducing the current of corrosion in case of laser modification process. Wear resistance of laser modified specimens was improved in comparison to diffusion boronized layers.

Microstructure and selected properties of Monel 400 alloy after laser heat treatment and laser boriding using diode laser

“…For low laser beam scanning velocity equal to 5 m/min, microhardness change is sharp between the coating and the substrate. This character of microhardness distribution was also reported in some papers on laser boriding [8,14,16]. On the other hand, if higher laser beam scanning velocity is applied for the process, microhardness values decrease continuously with increasing the distance from the surface.…”

“…Moreover, surfaces become more smooth if laser scanning speed is higher during the process. This effect results from lesser degree of mixing molten pool if exposure time of laser beam is shorter and was noted in previous research [8].…”

“…In this process, boron atoms diffuse into the substrate to form metallic borides of high hardness [5,6]. Depending on the substrate material, boriding is also carried out to increase the corrosion resistance [7,8]. Current research focuses on boriding of iron alloys [5][6][7][8][9] and, in addition, titanium and its alloys [10], niobium, chromium, tungsten [11], and nickel alloys [12][13][14][15].…”

“…Depending on the substrate material, boriding is also carried out to increase the corrosion resistance [7,8]. Current research focuses on boriding of iron alloys [5][6][7][8][9] and, in addition, titanium and its alloys [10], niobium, chromium, tungsten [11], and nickel alloys [12][13][14][15]. Boriding of nickel alloys leads to obtaining microstructure consisting of nickel boride mixture with borides of other metals, depending on the type of an alloy, e.g., during boron laser alloying of Inconel or Nimonic alloys, mixtures of nickel and chromium borides are formed.…”

Adhesive Behavior of the Pack-Borided AISI 304L Steel with Microwave Hybrid Heating

“…In their study, Alias et al [3] increased the surface hardness of AISI 304 austenitic stainless steel alloy 5 times with the pack-boriding process at 850 °C and for 8 hours. In many studies in the literature, high surface hardness values have been obtained in different types of steels as well as austenitic stainless steels by applying boriding process [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Thanks to boriding, the surface hardness of the material not only increases; since the chemical reactivity of boron against oxygen is high, a thin oxide film forms on the boride layer.…”